SK453690A3 - Record carrier, method of and information recording device for obtaining such record carriers, and information recording device comprising anti-copy means to inhibit unauthorized copying - Google Patents

Abstract

A record carrier is disclosed carrying subcode information in addition to the main information. The subcode information comprises "copy" bits of alternating logic values to indicate that the recorded information is a copy. Moreover, a method and recording device (72) for obtaining such record carriers are described. Finally, a recording device (71; 72) is described, which comprises a detection circuit (85) which detects the presence of "copy" bits of alternating logic values in the received information, and which comprises a decision circuit (94; 95) for deciding whether recording of the received inforrnation is allowed depending upon the detection of the presence of the "copy" bits of alternating logic values.

Description

The invention relates to a record carrier carrying the main information together with a series of subcode frames that comprise each copy bit. The invention further relates to a method of obtaining such a record carrier, wherein information is recorded thereon together with a plurality of subcode frames comprising each copy bit. Further, the invention relates to an information recording apparatus for obtaining a record carrier which is designed to record the master information together with a series of subcode frames comprising each copy bit on the record carrier. Finally, the invention relates to an apparatus for recording information received together with a series of subcode frames containing each copy bit, the apparatus comprising a copy protection means to prevent unauthorized copies of the received information being made. The security means comprises a decision means for deciding whether recording of the received information is permissible depending on the logical values of the received copy bits, and a means sensitive to deciding that, when recording is not permissible, it prevents recording.

BACKGROUND OF THE INVENTION

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Record carriers with audio information in digital form have been available for a considerable time. Such a record carrier may be, for example, an optically readable disc, such as a compact disc, or a magnetic tape, such as DAT-type cassette tapes. The advantage of digitized audio information is its extremely high quality. Another feature of the digitized information is that it can be copied to an almost unchanged extent without significant loss of quality.

This latter feature constitutes a major problem when marketing consumer equipment by means of which digital audio information can be not only reproduced but also recorded. This is because such a device allows consumers to widely infringe copyright by making the content of the record carrier carrying the digitized audio information easy to copy.

Since there is no loss of quality as a result of copying, the customer hardly has any reason to buy a relatively expensive original that is subject to copyright protection if an original or a copy is available. All of this leads to a substantial loss of copyright revenue.

A recently introduced copy protection method is known which alleviates these disadvantages, such as the Solocopy protection system. This system allows only the first generation copies to be made from record carriers carrying original information. In the copy protection system Solocopy, it is assumed that the digital information to be recorded conforms to a standard audio-interface format as described, for example, in the first edition (1989.03) of IEC-958. Such a format includes the main and secondary code feeds. The subcode information signal includes a copy bit indicating whether the information can be freely copied and a category code indicating the source of the recorded information.

In accordance with the Solocopy copy protection method, it is determined by the category code and the copy bit whether the information supplied can be copied. For example, copying is always allowed when the category code indicates that the information is coming from the CD player. This is based on the assumption that the CD player is capable of playing compact discs for playback only. In the meantime, however, devices have been developed by which information on a record carrier can be recorded, which can later be read by a standard CD player for reading compact discs intended only for playback. The known protection by the Solocopy system therefore does not prevent copying of the information recorded on the optical record carrier capable of repeatedly receiving the record.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a means for alleviating the aforementioned drawback.

According to a first feature of the invention, the record carrier of the type mentioned above is characterized in that the logical value of the copy bits is alternated in successive subcode frames.

A method of the type mentioned above for obtaining the record carrier according to the invention consists in that during recording, logical values are allocated to the copy bits of consecutive subcode frames in accordance with the alternating combination.

An apparatus of the above type for obtaining record carriers according to the invention consists in providing allocation means for allocating logical values in accordance with an alternating combination with a copy bit of consecutive secondary code frames of the information to be recorded.

Recording of copied bits with alternate logical values falls within the scope of a standard CD-ROM system for digital audio recording, so that it remains possible for record carriers to be captured by existing CD players. When the standard CD information is recorded on a record carrier capable of repeatedly receiving a record, it is possible to indicate in the recorded information that the information recorded on the respective record carrier is a copy using the alternate logical value of the copy bit without adversely affecting the information acquisition process by standard CD player.

The use of alternating combinations of different shapes allows the copy number to be specified in the copy cycle. For example, if the copy protection method allows both first-generation and second-generation copies to be made, it is possible to distinguish between copies of the first generation, the second generation and the higher generations.

Information combinations that are very convenient due to their simplicity and which make it possible to specify a generation number are periodic combinations in which the generation number is represented by the duty cycle of the combination, i. the ratio between the number of copy bits of the first logical value in a period and the total number of copy bits in that period.

In accordance with a second aspect of the invention, copying of the record carrier according to the invention can be prevented in a very simple manner by using a master information recording apparatus which is received together with a series of subcode frames containing each copy bit, the apparatus comprising copying means to prevent unauthorized copying the received information. The security means comprises a decision means for deciding whether recording of the received information is allowed depending on the logical value of the received copy bits, and a means sensitive to deciding that the recording is not allowed to prevent recording, the apparatus being characterized by comprising detection means for detecting the alternation combination in the logical values of the recorded copy bits, wherein, the decision means is adapted to decide whether recording is allowed depending on the detection of the alternation combination.

This device has the advantage that the information to be recorded can be transmitted directly in the format prescribed by the IRC-958 digital-audio-interface standard, without the additional steps required during reading the information. In accordance with this standard, the logical value of the copy bit in the secondary code for the digital-audio-in5 terfac standard is equalized to the copy bit of the information source, i. in this case, a copy bit of information read from the record carrier in the reading device.

By detecting the different rotation combinations, it is then possible to distinguish between first generation copies and higher generation copies when deciding whether or not the recording is allowed or not.

The recording apparatus may comprise a device designed to make recordings on a record carrier of another type, for example a DAT-type tape cassette from which the information originates, for example a compact disc capable of receiving a repeated recording.

If the recording device is intended to record information on a record carrier of the same type from which the information having the alternate logic value of the copy bit originates, it is desirable to provide the recording device with the means that the copying bits with the alternate logic values are recorded.

BRIEF DESCRIPTION OF THE DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS The invention is explained in more detail below with reference to the accompanying drawings, in which: FIG. 1 and 2 show a schematic representation of a standard CD signal format, FIG. 3 and 4 are a graphical representation of possible shapes of an alternating combination of logical values of copy bits for a record carrier according to the invention; 5 shows a block diagram of an information recording apparatus according to the invention, FIG. 6 is a block diagram of a detail of a circuit for use in the information recording apparatus shown in FIG. 5, FIG. 7 is a block diagram of an information copying system using a recording apparatus according to the invention; FIG. 8 is a detail of a detection circuit for use in the recording devices of the information shown in FIG. 7 and FIG. 9 is a flow chart of a program for determining whether recording of received information is allowed or not allowed.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 shows a digital signal data format in accordance with a CD standard. Such a signal is divided into blocks having 98 frames each. Each frame contains data bits (DB) representing the main information (MAIN DATA) and the subcode DATA information. The subcode information within frames 2 to 97 includes 8 bits of subcode for each frame. The subcode bits in the block form the subcode frames of the subcode channels P to W, each subcode frame containing 96 bits.

Fig. 2 shows the secondary code frame format of the secondary code channel Q. This secondary code frame includes a four bit control group including one bit referred to as a copy bit. The logical value of the copy bit indicates whether the associated master information can be freely copied. For a well-known compact disc, the logical value of the copy bit is the same throughout the disk, meaning that in each secondary code frame on the compact disc, the copy bit has a logical value of 1 or a logical value of 0.

In the case of the record carrier according to the invention, the logical values of the copy bits are alternated, for example, as shown in FIG. 3 and FIG. 4, to indicate that the recorded information is a copy.

In the case of the alternating combination shown in FIG. 3, the values of the copy bits alternate periodically, alternating four subcode frames containing each copy bit having a logical value of 0 each with four subcode frames containing each copy bit having a logical value of 1.

In FIG. 4, the logical values of the copy bits also change periodically, but here, six subcode frames containing a logical value of 0 alternate with two subcode frames each containing the copy bits of the logical value.

First

Recording of various alternating combinations of different shapes as shown in FIG. 3 and 4 also provides the possibility to indicate on the record carrier whether it is a copy of a first generation or whether it is a copy of a second or higher generation.

In the alternating combinations shown in FIG. 3 and 4, the duty cycle is the ratio between the number of copy bits of a logical value of 0 in a period with the total number of bits in each period of the alternating combination.

It will be apparent to those skilled in the art that the rotation combinations may also indicate the copy number in the copy cycle in different ways, for example, periodic rotation combinations of different lengths of time.

By using appropriate coding without the unidirectional logical value component of the copy bits, it is also possible to transmit the generation number information and, if necessary, other information via the copy bit. Transferring information using the alternating logical value of the copy bit has the advantage that this remains within the CD standard. This means that information can be read using a standard CD player.

Fig. 5 illustrates an embodiment of a recording apparatus for obtaining a record carrier on which the logical values of the copy bits alternate. The recording equipment comprises a cascade connection of the CIRC 50 encoder and the EFM 51 modulator for converting the incoming digital information originating, for example, from an analog-to-digital converter, into a format prescribed by the CD standard. The EFM modulator 51 provides an output signal of this format to a control circuit 52 for an optical recording head 53 arranged opposite to a rotating record carrier 54 capable of receiving a recording. The recording apparatus further comprises a circuit 55 for generating a clock signal for controlling the CIRC encoder 50 and the RFM modulator 51. The EFM further comprises inputs for supplying the secondary code information to the EFM. The logic value of the copy bit to be recorded is fed to the modulator 51 by the EFM circuit 57 through the signal line 56. The circuit 57 provides a periodic signal to the EFM modulator. For example, the periodic signal may be derived by frequency division from a clock signal that is routed to the circuit 57 by the clock generating circuit 55 over the signal line 58.

Fig. 6 illustrates another embodiment of circuit 57 allowing a specific shape alternate combination to be selected from a series of alternate shape alternate combinations. For this purpose, circuit 56 includes a circuit 60 that derives a series of signals having alternating combinations of different shapes, for example, alternating combinations having different duty cycles, from a clock signal fed over signal line 58. These signals are fed to a selection circuit 61 which carries one of signals to the signal line 56 depending on the control signal Vs.

Since the alternating logical values of the copy bits on the record carrier indicate that the information being recorded is a copy, further copying can be prevented by simply detecting whether the logical values of the copying bits in the information to be recorded are rotated and recording is prevented if the copying bits of the alternate logical ones are detected. values.

Fig. 7 shows an embodiment of a system for copying information in which this is realized. The information copying system comprises an optical reading device 70 for reading optical discs, a magnetic recording device 71 and an optical recording device 72 for recording information read by the reading device 70.

The reading device 70 is of the conventional type adapted to read CD information from the optical record carrier 73. For this purpose, the reading device 70 comprises an optical reading head which is connected to the cascade connection of a conventional CIRC decoding circuit 75 and an EFM demodulator 76, which forms, for example, part of the SAA 7210 type integrated circuit supplied by PHILIPS. Such an EFM demodulator 76 generates two digitized stereo audio information signals and a subcode signal at its outputs. These signals are fed to a formatting circuit 77, for example of the type SAA 7220, which converts the received information into the format prescribed by the digital-audio-interface standard (IEC 950). This digital-audio-interface format comprises blocks 192 of main information frames and a series of secondary code interface frames. These subcode frames include each interface copy bit whose logical value, in accordance with the digital-audio-interface standard, is taken from the copy bit in the subcode information in the read information.

The output signal conforming to the digital-audio-interface standard is fed to the devices 71 and 72. The received information is read into the reformatting circuits 78 of the reader The reformatting circuits 78 transmit a format suitable for processing by the recording devices 71 and 72.

The reforming circuitry may be, for example, an SX 23053 integrated circuit supplied by SONY. This type of reformatting circuit generates main information and subcode information at its outputs. The circuit further includes an output to which the copy bit information CB relating to the logical value of the received interface copy bit is provided and an output to which a block synchronization signal BS is provided to indicate the beginning of each received digital-audio-interface block.

In the magnetic recording apparatus 71, the information supplied by the reformatting circuit 78 is fed to a circuit 79 of the conventional type for driving the magnetic head system 80 for recording the received information on a DAT-type tape cassette 81. Similarly, the information supplied by the reformatting circuit 78 to the optical recording device is fed to a circuit 82 of the conventional type, which includes, for example, an EFM and an encoder ο.

An OIRC for exaggerating the optical recording head 83 to record the received information on the optical record carrier 84. In the recording devices 71 and 72, the copy bit information CB and the block sync signals BS supplied by the reformatting circuit 78 are fed to the detection circuit 85 to determine whether the logical value of the received copy bit information is alternating. The detection circuit 85 provides a detection signal Vd. if the alternating logical value of the interface of the copy bit is detected.

Fig. 8 illustrates an example of a detection circuit 85 comprising three clock controlled flip-flops D 90, 91 and 92. The block sync signal BS provided by the reformatting circuit is guided by the clock inputs of flip-flops 90, 91 and 92. The copy bit information CB is routed to the flip data data input. The output of flip-flop 90 is connected to the data input of flip-flop 91 and to the exclusive sum gate 93. The second exclusive sum gate 93 input is connected to the flip-flop output 91. The exclusive sum gate output 93 is connected to the flip-flop 92 data input. The output signal at the output of the flip-flop 92 serves as a detection signal Vd.

The circuit shown in FIG. 8 works as follows. If the logical value of the interface copy bit changes, the logical value of the signal at the input of the flip-flop 91 when the first copy bit of the changed logical value reaches the input of the logical circuit 91 will no longer correspond to the logical value of the signal at the flip-flop output. This value is locked in the flip-flop 92. Subsequently, the detection signal Vd also acquires a logic value of 1.

In the recording device 71, the detection signal Vd is routed to the decision circuit 94. In addition, the secondary code information provided by the reformatting circuit 78 is routed to the decision circuit 94. Based on the received secondary code information and the detection signal Vd, the decision circuit 94 decides whether recording is allowed. received main information. If recording is not allowed, the decision circuit generates a control signal that is routed to the control circuit 79 along the signal line 5, the control circuit 79 being of the type that is discarded based on the control signal routed along the signal line so that information recording is prevented. For example, the decision circuit 94 may include a microcomputer filled with a suitable program. Before this program is described in detail, the portion of the digital-audio-interface subcode information received for proper understanding will be described

Of particular importance is the secondary code channel C of the digital-audio-interface format of the received secondary code information. This subcode channel C contains subcode frames of 192 bits. These secondary code frames indicate whether the information originates from a source intended for professional use. In addition, it is indicated whether the associated information originates from an audio source. In addition, for resources intended for consumer applications, channel C contains a category code indicating the source type. This may be, for example, a dual-channel compact disc audio system, a dual-channel digital audio player, and the like.

format, which is a decision criterion.

Fig. 9 is a flow chart of a decision program for determining whether recording of received information is allowed. This decision program is based on the decision program used in the Solocopy system. However, the program was modified to make decision-making dependent on logical values

I copy bits. In step S1, it is determined by the information from the subcode channel C whether the information originates from an information source intended for this, the recording is prevented. It checks whether the received information is audio-information. If not, recording is prevented at step S4. In step S5, it is checked whether the received category code appears in the list of known category codes. If this is not the case, the recording is enabled in step S6 and in addition information is recorded on the tape 81 to indicate that the information is a copy. If professional use. If it is in step S2. In step S3, the information is subsequently read, associated with a category code indicating that the record is not allowed. However, the manner in which this proceeds is outside the scope of the invention and is therefore not described in detail.

In step S7, it is checked whether the information comes from an analog-to-digital converter. If so, the recording is enabled in step S8. In step S9, it is determined based on the received detection signal Vd whether the logical values of the interface copy bits alternate. If they alternate, recording is prevented in step S10, the received values In step S11, it is ascertained based on the received logical values of the copy bits whether the relevant information can be freely copied. If so, recording is enabled in step S12, and information indicating that the recording information can be freely copied is added.

In step S13, it is checked whether the category code specifies the source for which copying of the feed information is allowed. If so, copying is enabled in step S14. If not, copying is prevented at step S15.

The decision device 72 includes a decision circuit 98 that is largely identical to the decision circuit 94. When information is recorded that should never be copied again, the decision circuit 98 generates a control signal for the circuit 96 which causes the record copy bits of alternating logical values.

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For circuit 96, circuits 57 described above may be used. It is also possible to provide the circuit 72 with a detection circuit 97 for detecting the generation number of the copy cycle for the received information based on the shape of the alternating combination. The decision as to whether the received information can be recorded or not can be recorded can then be made based on the detected generation number of the information. For example, copying of a first generation copy may be allowed, but copying of a second generation is not allowed.

The circuit 98 should be adapted to produce a substitution pattern indicating a higher generation number than the detected generation number, depending on the detected generation number.

In the foregoing description, the invention has been explained for a record carrier carrying a standard CD signal having ripped copying bits to indicate that the recorded information is a copy. It should be noted, however, that the invention may in principle be applied to any other record carrier that carries, in addition to the master information, secondary code information including the copy bit.

Claims (17)

A record carrier carrying a master information together with a plurality of subcode frames carrying each copy bit, characterized in that the logical values of the copy bits of successive subcode frames are alternated. Record carrier according to claim 1, characterized in that the shape of the combination indicates the generation number of the information in the copy cycle. The record carrier of claim 2, wherein the detected combination is a periodic combination in which the ratio between the number of copy bits of the first logical value in a period and the total number of copy bits in said period indicates a generation number. The record carrier of claim 1 or 2, wherein the recorded standard CD signal is recorded. 3 the information is A method of obtaining a record carrier according to claim 1, 2, 3 or 4, wherein the master information is recorded together with a series of subcode frames each containing a copy bit, characterized in that during recording the copy bit of consecutive secondary frames is recorded. code assigns logical values, in accordance with the alternating combination. Method according to claim 5, characterized in that the information to be copied is previously recorded information, the shape of the alternating combination being dependent on the generation number of the previously recorded information. The method of claim 6, wherein the detected combination is a periodic combination, wherein the ratio between the number of copy bits of the first logical value in the period and the total number of copy bits in said period is selected depending on the generation number. The method of claim 5, 6 or 7, wherein the recorded information is a standard CD signal. An information recording apparatus for obtaining a record carrier according to claim 1, 2, 3, or 4, which is designed to be recorded on the record carrier of the master information together with a series of subcode frames comprising each copy bit, characterized in that it includes means for logical values in accordance with the alternating combination with a copy bit of consecutive secondary code frames of the information to be recorded. device allocation 10. The information recording apparatus of claim 9, wherein the allocation means comprises invoking means for selecting an alternate combination of a specific shape from a series of predetermined combinations of combinations depending on the control signal. The information recording apparatus of claim 10, wherein the fetching means is adapted to cause a periodic combination whose ratio between the number of copy bits of the first logical value in the period and the total number of copy bits in said period depends on the control signal. An apparatus for recording information according to claim 9, 10, or 11, characterized in that it is adapted to record standard CD signals. 13. An information recording apparatus comprising copy protection means for preventing unauthorized copying of received information, for recording main information received together with a series of subcode frames, each containing a copy bit, the security means including decision means for deciding whether recording of the received information is allowed depending on the logical value of the received copy bits and a means sensitive to deciding that the recording is not allowed to prevent recording, characterized in that it comprises a detection means for detecting the alternation combination in the logical values of the received copy bits of successive subcode frames, the decision means being adapted to decide whether recording is allowed, depending on the alternation combination. 14th 15th 16th 17th according to claim 13, the detecting means of combinations of different ones determines whether it is detected on the shape An apparatus for recording information, characterized in that it is adapted to detect alternating shapes, and is adapted to enable recording depending on the alternating combination. The information recording apparatus of claim 14, wherein the detecting means is adapted to detect in a period of a periodically alternating combination of the ratio between the number of copy bits of the first logical value and the total number of copy bits in said period, the decision means adapted to decide whether recording is allowed, depending on the ratio found. The apparatus for recording information according to claim 13, 14 or 15 for recording the master information together with a series of second subcode frames comprising each second copy bit, characterized in that the device comprises allocation means for assigning logical values to the second copy bits of consecutive second copies. secondary code frames in accordance with the alternation combination. Information recording apparatus according to claims 14 and 16, characterized in that the allocator for allocating the logical values of the bit in accordance with the combination, whose alternating combination indicating the alternate is adapted to the second copy shape depends on the shape found in the logical values of the copy frames of the received information. bits in others 18. The information recording apparatus of claim 15 and 17, wherein the allocation means is adapted to assign logical values to the second copy bit in accordance with the periodic combination, wherein the ratio between the first copy bits of the first logical value in the period and the total number of second copy bits. in the said period it is dependent on the observed ratio.